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The prefix of "obtrusive" is "ob-".
1. having or showing a disposition to obtrude, as by imposing oneself or one's opinions on others.
2. (of a thing) obtruding itself: an obtrusive error.
3. protruding; projecting.
Obtrusive and unobtrusive are opposites. Obtrusive means obvious, and unobtrusive means not obvious.
Most Arabic teachers are obtrusive.
I could not see around the corner because he obtrusive sign was blocking my view